1. Field of the Invention
The present invention relates to a rotary transfer system of a blow molding machine to be used for molding a container for packaging such as a bottle.
2. Detailed Description of the Prior Art
On a molding machine for intermittently transferring an injection-molded preform up to a stretch-blowing position by holding a mouth part or the like, a hydraulically operated actuator has conventionally been used as a rotary drive source.
An actuator driven by a hydraulic drive source has had such problems as it needs piping, valves, or the like; it has had restriction in the operation because the hydraulic source is commonly used as other drive sources; further, oil leakage may occur; and it has taken time also for maintenance and control as a result.
For the above reasons, it is considered to use an electric servo motor (hereafter, called servo motor) as it is, which is adopted for use in an insert molding machine, and to perform rotary transfer of the transfer member of the rotary board, however, the transfer member is supported on the supporting board above the machine base so as to freely rotate and a plurality of metal molds are attached to the undersurface of the transfer member, in the case of the blow molding machine, therefore, differing from the case of the insert molding machine which rotatively transfers a rotary disc supported by the machine base from underneath, the weight of the transfer member is apt to be concentrated on the rotary shaft and has also large inertia, therefore, a rotational torque larger than ever is required for intermittently rotating the transfer member smoothly, and a rotary transfer device with a larger torque is required as a result.
Moreover, although it is easily possible to increase an output torque by means of a variable-speed gear, it is very difficult to further secure an installation space for the variable-speed gear in the case of a small and middle type of a molding machine, while it is easy in the case of a large type of a molding machine though. For this reason, it has been desired to develop a rotary transfer device with a large torque eliminating the need for the variable-speed gear.
The present invention is devised from the above-described situation, and the purpose thereof is to provide a rotary transfer device with a rotary transfer device of a new structure capable of intermittently rotating the transfer member directly by the servo motor.